The present invention generally relates to the field of oximeter sensors and, more particularly, to oximeter sensors having a laminated construction.
Information on the amount of oxygen within blood or more preferably a blood flow is desirable in many instances. This is often characterized as the oxygen content or oxygen saturation of the blood. Oximeters are able to provide this type of information and are generally well known in the art. Patient data that is used by the oximeter to determine the oxygen content/saturation is monitored/measured by an oximeter sensor that operatively interfaces with the oximeter. There are at least generally two types of oximeter sensorsxe2x80x94invasive and non-invasive. Invasive oximeter sensors are installed within the body through an appropriate aperture. Non-invasive oximeter sensors are installed on the exterior skin of an appropriate body part such as a finger or a foot.
Oximeter sensors typically employ a pair of light sources that emit light at different wavelengths, as well as one or more optical detectors. The power for the emitter and the oximeter signal from the detector are transmitted between the sensor head and the oximeter via a round multiple conductor cable. A round cable is the preferred configuration for conductor shielding and for cable manufacture. Electrical signals are provided by the oximeter to the oximeter sensor to operate the light sources in a predetermined manner (e.g., each light source is xe2x80x9cpulsedxe2x80x9d in accordance with a predetermined pattern). Light from each of the light sources will either be absorbed by the blood or will pass entirely through the patient""s tissue and blood for receipt by the detector(s). Electrical signals from the detector(s) are provided back to the oximeter. Information on how the light sources are being operated, the wavelengths of these two light sources, and the amount of light which passes through the blood to the detector(s) are all used by the oximeter to calculate the oxygen content/saturation of the blood. This information will then typically be displayed for review by appropriate personnel.
Various factors contribute to the overall commercial success of a given oximeter sensor. One is its cost. Another is its comfort when positioned on the relevant body part. It would be desirable to have an oximeter sensor the could be made within certain cost constraints. It would also be desirable to have an oximeter sensor that provided at least a certain degree of patient comfort and would not cause breakdown of the patient""s skin when worn for long periods of time. Enhanced patient comfort can be realized by things such as the size, shape, and weight of the oximeter sensor, as well as the having the oximeter sensor interface with the patient so as to at least reduce the potential for the development of xe2x80x9cpressure points.xe2x80x9d Uneven distribution of the forces being exerted on the patient by the oximeter sensor can contribute to the development of undesired soreness and possibly pressure necrosis on the patient""s skin surface.
The present invention generally relates to an oximeter sensor which utilizes a laminated construction and which provides a flat sensor/patient interface over at least those portions of the oximeter sensor housing which include an oximeter sensor cable. The oximeter sensor cable is used to establish an operative interface with an appropriate oximeter. Another way of characterizing the present invention is that it is directed to how a round oximeter sensor cable is interfaced with the patient""s sensor site.
A first aspect of the present invention is embodied in an oximeter sensor that includes a laminated sensor housing. This laminated sensor housing is defined by first and second film assemblies which are appropriately interconnected, with the first film assembly the being that portion of the sensor housing that projects toward a body portion on which the oximeter sensor is mounted. Interconnection of the first and second film assemblies is provided by an appropriate seal, such as a heat seal or an integral adhesive film. In any case, each of the first and second film assemblies include at least one film. That is, one or both of the first and second film assemblies may in fact be defined by a plurality of individual films which may be interconnected by one or more of the above-noted techniques. It should be noted that each film within the first film assembly and each film within the second film assembly need not necessarily by of the same size, thickness, and/or shape. In one embodiment, the maximum thickness of each individual film in the first and second film assemblies is about 0.01 to about 0.04 inches.
The oximeter sensor of the first aspect of the present invention also includes an emitter assembly (e.g., one or more light sources and including a pair of light sources that emit light at different wavelengths) and a detector assembly which are each disposed between the first and second film assemblies within the oximeter sensor housing. A cable is electrically interconnected with both the emitter assembly and the detector assembly. This cable is also either connected with an oximeter or is at least interconnectable with an oximeter (directly or through one or more intermediate cables and an appropriate connector(s)). Part of this cable extends between the first and second film assemblies such that an end portion of the cable is actually disposed within the sensor housing. Notwithstanding this positioning of the cable within the sensor housing in this manner, that portion of the first film assembly which overlies this portion of the cable remains at least substantially flat. Having this type of flat profile in a laminated sensor housing construction reduces pressure concentrations and thereby enhances patient comfort.
Various refinements exist of the features noted in relation to the first aspect of the present invention. Further features may also be incorporated in the first aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. The flat interface between that portion of the sensor housing which contains the cable and the body portion on which the oximeter sensor is installed is realized notwithstanding the fact that the cable is disposed within a sensor housing of a laminated construction. This cable is subject to a number of characterizations. One is that the cable is something more than a flat connector or the like. In one embodiment, the vertical extent or thickness of the cable is at least about 0.030 inches. One or more individual electrical conductors (e.g., wires) may collectively define the cable. Typically a single encasement (e.g., a piece of rubber tubing or the like) will be disposed about these plurality of individual electrical conductors, and this encasement may be of at least a generally circular cross section with a diameter that is within a range of about 0.070 inches to about 0.180 inches. The location where the cable exits the oximeter sensor housing is also relatively xe2x80x9cclosexe2x80x9d to where the emitter or detector assembly is disposed. Consider the case where the emitter and detector assemblies are disposed along a first reference axis within the sensor housing, and where the cable extends within the oximeter sensor housing at least generally perpendicular to this first reference axis. In one embodiment, the distance between this first reference axis and the location where the cable actually exits the oximeter sensor housing, measured perpendicularly to the noted first reference axis, is no more than about 0.75 inches.
There are a number of ways of characterizing the interface between the cable and the first film assembly which again is that portion of the sensor housing which interfaces with the body portion on which the oximeter sensor is mounted. One way of characterizing this interface is that the contact between the first film assembly and the cable is at least substantially limited to being along and defining a line. Another way of characterizing this interface is that the first film assembly is not xe2x80x9cwrappedxe2x80x9d around the outer perimeter of the cable. Yet another way of characterizing this interface is that the first film assembly is tangent to the perimeter of the cable.
The flat profile for the first film assembly in the region where the cable is disposed within the sensor housing may be realized by incorporating one or more supports within the sensor housing that have a surface that is disposed in engagement with the first film assembly and that is at least substantially flat or planar. Once again, the first film assembly is that portion of the sensor housing which interfaces with the body portion on which the oximeter sensor is mounted. Any such support may have any number of characteristics. For instance, this support(s) may be formed of a compressible material that has a compression range of about 7 psi to about 25 psi for realizing about a 50% compression of the associated support(s). Representative materials having this characteristic include various types of foams, and low durometer thermoplastics and thermoset plastics.
The above-noted support(s) for providing a flat profile on that portion of the sensor housing which includes the cable will typically extend along at least substantially the entire length of that portion of the cable that is disposed within the oximeter sensor housing. In one embodiment, a support is disposed along at least one and more preferably along both sides of that portion of the cable that is disposed in the sensor housing, and further is preferably disposed in abutting engagement with this portion of the cable. Although the support could xe2x80x9ccradlexe2x80x9d the cable to maintain the cable and first film assembly in spaced relation, there may be a slot of sorts disposed between/defined by the above-noted pair of supports so as to allow the cable to actually contact the first film assembly. Preferably the first film assembly is only tangent to the cable on its xe2x80x9clowerxe2x80x9d extreme in this case and as noted above.
There are certain size-related features that may be incorporated into the above-noted support(s). Preferably there is a sufficient amount of the flat surface of that portion of the support that interfaces with the first film assembly so as to realize the desired effect of reducing pressure concentrations on the body portion over that portion of the sensor housing which contains the cable. In one embodiment, the minimum surface area of that portion of the support that interfaces with the first film assembly to provide the desired flat profile is about 0.05 in2. Consider the embodiment where a pair of supports are disposed in spaced relation such that the cable may be disposed therebetween and engage the first film assembly along at least substantially a line. In this case the surface area of that portion of each of the supports which is disposed alongside the cable, which is flat, and which engages the first film assembly is at least about 0.025 in2. Another way of characterizing the flat interface provided by that surface of the support(s) that engages the first film assembly is by its lateral extent. xe2x80x9cLateralxe2x80x9d in this context means measured generally perpendicular to the length dimension or longitudinal extent of the cable. In one embodiment, the flat surface of the each support extends beyond each side of the cable by a distance that is equal to at least about xc2xd the diameter of the cable. xe2x80x9cBeyond the sidexe2x80x9d means that this measurement is from a reference plane that is both tangent to the cable and perpendicular to the first film assembly, and is taken perpendicularly to this reference plane.
Another size-related feature of the support(s) is its height or thickness. Each support may extend between and interface with each of the first and second film assemblies, as may the cable. However, the support(s) is preferably of a lesser vertical extent than the cable. In one embodiment, the thickness or height of any support disposed proximate to the cable for providing the flat profile on the lower surface of the sensor housing is less than the diameter of this cable, but is greater than ⅓ of the diameter of the cable. Therefore, the second film assembly may xe2x80x9cbulgexe2x80x9d somewhat over that region of the sensor housing which contains with the cable.
The above-noted support(s) may be in the form of a preform or the like that is disposed between the first and second film assemblies. This preform may include a cable aperture for receiving the cable. This preform may also be a least generally L-shaped, with the cable being disposed in one leg of the xe2x80x9cLxe2x80x9d and with the emitter and detector assemblies being disposed within apertures formed in the other leg of the xe2x80x9cL.xe2x80x9d Both the cable aperture, as well as the emitter and detector assembly apertures, may extend through the entire vertical extent or thickness of the preform. In one embodiment, the cable aperture is in the form of a slot that extends at least generally along a first reference axis, a first aperture for either the emitter or detector assembly is disposed on an end of this slot, a second aperture for the other of the emitter and detector assemblies is disposed in spaced relation to the first aperture, the first and second apertures are disposed along a second reference axis that is disposed at an angle relative to the first reference axis (e.g., 90 degrees to provide the above-noted xe2x80x9cL-shapedxe2x80x9d configuration), the preform is severed along the second reference axis between the first and second apertures, and each of the cable aperture, the first and second apertures, and the interconnecting cut between the first and second apertures extend through the entire vertical extent of the preform.
Other options exist for providing a flat interface between the oximeter sensor housing and the adjacent body portion along/over that portion of the sensor housing which contains the cable. The manner in which the first and second film assemblies are interconnected has an effect on the interface between the oximeter sensor housing and the body portion, or more specifically the profile of the first film assembly in that region of the sensor housing which contains the cable. In one embodiment, the first and second film assemblies are interconnected by least one seal. That portion out of the seal where the cable exits the oximeter sensor housing is disposed at least substantially coplanar with the interface between the cable and the first film assembly. Stated another way, there would be first and second seals between the first and second film assemblies on the opposite sides of the cable where the cable exits of the oximeter sensor housing. A reference plane that interconnects the first and second seals in this region would preferably be tangent to the cable, but at a minimum would be disposed at an elevation that was closer to that portion of the cable which interfaced with the first film assembly than the center of the cable. Yet another way of characterizing the first and second film assemblies where the cable exits the sensor housing is that the first film assembly is at least substantially flat and the second film assembly is at least generally U-shaped for providing a U-shaped aperture for receiving the cable.